Generally, in structures such as buildings or apartments, windows are mainly used to ventilate contaminated indoor air. However, such a ventilation method is disadvantageous in that outdoor air is rapidly drawn indoors and air conditioned indoor air is easily exhausted through a window. This results in low thermal efficiency.
In an effort to overcome the above-mentioned problem, a hybrid ventilation apparatus is proposed in Korean Patent Registration No. 0964979.
In this conventional technique, a mounting plate having a through hole is installed in a housing. An on-off plate having a through hole therein is provided on the mounting plate. When the on-off plate is operated by a motor so that the through hole of the on-off plate is aligned and communicated with the through hole of the mounting plate, natural ventilation is conducted. Forced ventilation is carried out in such a way that indoor air and outdoor air are drawn by a supply fan and an exhaust fan, a heat exchanger exchanges heat between the indoor air and outdoor air, and then the heat exchanged air is discharged indoors and outdoors.
As such, in the conventional technique, when natural ventilation is required, the motor is operated to horizontally communicate the through hole of the mounting plate with the through hole of the on-off plate. However, it is impossible for a user to adjust the degree of opening of the through holes depending on airflow conditions. Therefore, the conventional apparatus cannot cope with strong wind. In the event of rain, rainwater may enter the housing, thus causing a malfunction of the apparatus. Furthermore, because low temperature outdoor air is directly drawn indoors and the temperature of indoor air rapidly decreases, there is a problem of low thermal efficiency.
In addition, the heat exchanger is installed on a base plate and is brought into contact with a sidewall of the housing that is disposed outdoors. Therefore, high or low temperature outdoor air is directly applied to the heat exchanger. Thereby, heat exchange efficiency of the heat exchanger is markedly reduced. Moreover, a severe dew condensation phenomenon is caused, and mildew forms, thus affecting the health of the user. Furthermore, a filter can filter out coarse dust from outdoor air but cannot remove fine dust such as yellow dust. If such fine dust enters the heat exchanger and contaminates it, the lifetime thereof is reduced. Furthermore, because the total heat exchanger contracts and expands depending on the variation in temperature of outdoor air, the airtightness cannot be ensured. As a result, the product reliability is markedly reduced, considering characteristics of the apparatus in which supply of air and exhaust of air are conducted at the same time.